关于LED单灯正向电压VF不良的探讨

文章基于LED芯片和LED单灯的工作原理和制程工艺，探讨了LED芯片封装以后正向电压K升高和降低的常见原因，并提出了改善措施。对于GaN基双电极芯片，由于芯片工艺制程或后续封装工艺因素，造成芯片表面镀层（ITO或Ni／Au）与P—GaN外延层之间的结合被破坏，欧姆接触电阻变大。对于GaAS基单电极芯片，由于封装材料和工艺因素，导致芯片背金（N—electrode）与银胶，或银胶与支架之间的接触电阻变大，从而LED正向电压VF升高。LED正向电压VF降低最常见的原因为芯片PN结被ESD或外界大电流损伤或软击穿，反向漏电过大，失去了二极管固有的I-V特性。

Discussion about LED Lamp Forward Voltage VF Failure

Base on the principle and manufacture technology of LED Chip & LED Lamp,the article discussed the common reason which LED lamp forward voltage VF will increase or reduce after beening packaged,then pro-posed the improvement measure.For GaN-based dual-pad chip,because of LED chip process technology and packaging technology,the contact between surface deposited layer(ITO Layer or Ni/Au Layer) and P-GaN epitaxial layer is damaged,the resistance of Ohmic-contact is become larger,so the LED forward voltage increased.For GaAs-based single-pad chip,because of packaging materials and process technology,the con-tact resistance between chip backing gold film(N eletrode) and silver-glue(or between silver-glue and lead-frame) become larger,there by increasing LED forward voltage.The most common reason for LED forward voltage reduce is that chip PN-junction was damaged or soft brokedown by ESD or other external high current,resulting in large reverse leakage current,lose diode intrinsic I-V characteristic.